Solid state switch construction

ABSTRACT

A solid state switch construction employing a saturable magnetic core switch. The switch has a keystem of magnetic material to change the magnetic property of the saturable magnetic core to effect switching of the signal information by transformer coupling. The keystem has a pair of legs extending on opposite sides of the magnetic core with two permanent magnets secured thereto. When the keystem is not depressed the magnets are located adjacent opposite sides of the core so that the magnetic flux path is formed through the magnetic core, the keystem, and the two permanent magnets to thereby saturate the magnetic core and prevent transformer coupling. When the keystem is depressed, the permanent magnets are moved away from the magnetic core to unsaturate it and variations in the magnetic field effect witching of signal information. The magnetic core is readily removable from the key construction without electrically disconnecting the leads from the circuitry to which they are connected should a malfunction of the switch body or keystem occur. The magnetic core is firmly but removably held within the switch body by a metal clip.

United States Patent Madland 1 Jan. 30, 1973 [54} SOLID STATE SWITCH[57] ABSTRACT CONSTRUCTION A solid state switch construction employing asatura- [75] Inventor: Robert C. Madland, Prospect, [IL ble magneticcore switch. The switch has a keystem of magnetic material to change themagnetic property of [73] Asslgnee' Tool works Chicago the saturablemagnetic core to effect switching of the signal information bytransformer coupling. The

[22] Filed: Nov. 18, 1971 keystem has a pair of legs extending onopposite sides I of the magnetic core with two permanent magnets [2]]Appl' l99872 secured thereto. When the keystem is not depressed themagnets are located adjacent opposite sides of the U.S. core so that themagnetic flux path is formed through [5 the magnetic core the keystemand the two per- Fleld Search 197/98; l79/90l C; manent magnets tothereby saturate the magnetic core 340/365 347 and prevent transformercoupling. When the keystem is depressed, the permanentmagnets are movedaway References cued from the magnetic core to unsaturate it andvariations UNITED STATES PATENTS 3,035,253 5/l962 Devol ..340/365 X 3,ll9,996 1/1964 Comstock 3,l60,875 l2/l964 Bernard Primary'ExamirterGeorge Harris Attorney-Roy H. Olson et al.

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9 Claims, 9 Drawing Figures lll 'J Patented Jan. 30, 1973 2 Sheets-Sheet1 Patent Jan. 30, 1173 3,714,611

2 Sheets-Sheet 2 -31 N mhl. Hlhl. K

SOLID STATE SWITCH CONSTRUCTION BACKGROUND OF THE INVENTION Thisinvention relates generally to a solid state switch construction, andmore particularly to a switch construction suitable for use in keyboardsutilized for feeding information into data processing equipment.

Keyboards are well known for use with data processing'equipment to feedin signal information corresponding to some particular code. Suchkeyboards may'take many forms, they being either provided withelectronic switches or mechanical switch components. One well known typeof keyboard comprises a plurality of electric switch contactsmechanically operated by depressing a keystem. The keystem may have acoded top face with a letter or number or the like. These devices suffermany disadvantages in that they are subject towear and the contacts tendto cause high resistance due to arcing or oxidization thereof. Also,atmospheric conditions may cause unreliable switching of thesecomponents due to dirt that may enter the keyboard.

More recently, solid state switches have been developed for suchkeyboards and have generally overcome the above disadvantages ofmechanically actuated electrical switch contacts. One form of solidstate switch comprises a permanent magnet and a core associatedtherewith. The permanent magnet, or the core, is fastened to a keystemor actuating member to move the core and magnet relative to one another.The core is generally provided with a drive winding wire and a sensewire threaded therethrough. An AC signal is applied to the drivewinding. .When the switch actuator is in the undepressed condition, thepermanent magnets are positioned on each side of the core and theeffective impedance is relatively low and no transformer coupling cantake place between the drive wire and the sense wire. When the actuatoris depressed, however, the permanent magnets move away from the core tounsaturate the core and substantially increase the AC impedance and.effect transformer coupling between the drive wire and the sense wire.While this type of switch construction overcomes the disadvantages ofprior keyboards for data processing equipment, it still suffersmechanical. failure of the switch body and the magnetic cores within theswitch body are not readily replaceable or interchangeable without ac-'tually unwiring or disconnecting the wires from the circuitry to whichthey are connected.

SUMMARY OF THE INVENTION Therefore, it is an object of this invention toprovide an improved solid state key construction wherein the magneticcore within the switch body is readily removable without disconnectingor removing the wires wound or threaded through the cores and a newswitchbody and actuating mechanism is easily connected to the existingmagnetic core while it remains connected to the keyboard.

Another object of this invention is to provide an improved solid stateswitch construction wherein the switch body is readily mounted intolarge keyboard assemblies for data processing equipment and whereinreplacement of defective switches is easily accomplished withoutunwiring the wires that are through the magnetic core within the switchbody.

. is readily accomplished.

The solid state switch construction of this invention is an improvementover application Ser. No. 879,220 filed on Nov. 24, 1969, now U.S. Pat.No. 3,638,221 which is assigned to the assignee of the presentapplication. As disclosed in this application a relatively large numberof switches are mounted in a housing to form a keyboard for dataprocessing equipment. Such keyboards are commonly used to feedinformation into the electronic circuitry of computers. Such computersrequire pulse signal information at rapid rates and over long periods oftime to do the necessary manipulation of the data and produce thedesired result. Therefore, keyboard switches are actuated substantiallycontinuously over long periods of time and are often in need of repair.One type of failure is that of the switch body components, they beingthe actuating mechanism itself or the arms carrying the permanentmagnets within the switch body. Since there is no movement of themagnetic core or the wires passed therethrough, failure of thiscomponent is indeed rare. Therefore, replacement of a defective switchrequires only that the switch body or actuating mechanism be removed anda new switch body and actuating mechanism positioned about the existingmagnetic core.

Briefly, the solid state switch construction of this in- .ventionincludes a magnetic core which is relatively loosely received within theswitch body and firmly but removably held therein by a small metal clip.The switch body is then inserted through a wall of a keyboard formounting the same in a conventional manner and the wires passing throughthe magnetic core is wired into the computer circuitry. Should failureoccur of the switch body components, the switch body components can beremoved from the keyboard housing without unwiring of the windingspassing through the magnetic core. To remove the switch body from thekeyboard housing, it is necessary to gain access to the underside of thekeyboard. This will allow removal of the small metal clip within theswitch body and allow the switch body to be pulled upwardly off of thetop wall of the keyboard housing and from about the magnetic core whichremains in place with its connected wires within the keyboard housing. Anew switch body is then inserted through the keyboard over the magneticcoil and the small metal clip is then inserted into the new switch bodyto assemble the switch body and magnetic core.

A further improvement of the switch construction of this invention isthat the retaining clip is of paramagnetic material and functions toprovide a magnetic shunt between thepermanent magnets to furthersubstantially aid in unsaturating the magnetic core so that AC signalcoupling can occur between the drive and sense wires about and throughthe core which may act as a transformer coupled device..

Other objects, features and advantages will become more fully apparentfrom the following detailed description when taken 'in conjunction withthe accompanying drawings wherein like reference numerals throughout thevarious views of the drawings areintended to designate similar elementsor components.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view of a solidstate key switch constructed in accordance with the principles of thisinvention;

FIG. 2 is a plan view of a portion of a keyboard illustrating four keyswitches extending upwardly therefrom to be actuated for applyingsignals to a data processing machine;

FIG. 3 is an elevational end view of the solid state switch extendingthrough the top wall of the keyboard housing and which shows, in phantomlines, the flexure of the switch body to remove a retaining clip fordisassembling a magnetic core member from the switch body;

FIG. 4 is an elevational side view of the solid state switch extendingthrough the top wall of a keyboard housing showing the magnetic coremember having the wires thereof extending outwardly for connection intoa circuit;

FIG. 5 is a view showing the switch body removed from the keyboard anddisassembled from the magnetic core which remains beneath the top wallof the keyboard housing;

FIG. 6 is an enlarged bottom view of the switch construction of FIG. 1showing the relative placement of the retainer clip and magnetic core;

FIG. 7 is a sectional view taken along line 7-7 of FIG. 6', and

FIGS. 8 and 9 illustrate the relative position of the permanent magnetswithin the switch body relative to the magnetic core for saturating andunsaturating the core to effect a switching action.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring now to FIG. 1, thereis seen an exploded view of a solid state switch constructed inaccordance with the principles of this invention and is designatedgenerally by reference numeral 10. The solid state switch 10 is formedofa switch body 12 into which is inserted a keystem 14 over a coilspring 16 which resiliently urges the keystem l4 upwardly in adeactuated condition when assembled. The keystem 14 is confined attheupper end by a top wall member 18 which is secured within a recess 19of the key body 12 by ultrasonically welding or other suitable means.

A pair of permanent magnets 20 and 22 are firmly held by spaced apartlegs 21 and 23, respectively, of the keystem l4 and are movabletherewith. The magnets 20 and 22 may be insert molded in the keystem.Mounted within the switch body 12, from the underside thereof, is amagnetic core member 24 having a drive wire 26 and sense wire 28extending therefrom and through recesses 30 formed in the end walls ofthe switch body.

Most advantageously, the magnetic core 24 is firmly but removably heldwithin the switch body by a removable clip 32 which frictionally engagesthe interior side walls of the switch body when assembled. Upon removalof the clip 32 the entire switch body structure can be removed from themagnetic core 24 and its associated wires 26 and 28 withoutnecessitating disconnecting of the leads from the-electric circuitry towhich they are connected.

state switches, each designated by reference numeral 10. The switches 10may be part of a switch matrix in a ten-by-ten, or any other suitable XYconfiguration, and may include indicia caps secured to the top of thekeystem 14 so that letters or numbers may be displayed.

FIG. 3 illustrates the switch 10 secured to the top wall 34 and furtherillustrates the side flexure of leg portions 38 and 40 in diametricallyopposed directions, as shown by the broken line, to allow simple removalof the clip 32 from within the recess 30. Once the clip 32 is removed,the holding tabs 33, FIG. 1, are squeezed together to remove the switchbody 12 upwardly and the magnetic core 24 can be dislodged from itsposition within the switch body 12 without requiring the disconnectionof the wires 26 and 28 from the circuits. This is best shown in FIGS. 4and 5. The switch 10 is shown in FIG. 4 with the magnetic core 24located between the permanent magnets 20 and 22 within the switch body12 and with the magnetic core 24 held firmly therein by the removableclip 32. The wires 26 and 28 extend outwardly of the switch body 12through the recesses 30, as best seen in FIGS. 1 and 3. FIG. 5 shows theswitch body 12, together with its keystem l4 and other associatedcomponents, completely removed from the top wall 34 of the keyboard sothat the magnetic core 24 and its associated wires 26 and 28 remainbelow the keyboard wall 34 in continuous electrical connection with itsassociated circuitry. Therefore, none of the electrical circuitry of thedata processing equipment is disturbed, and little or no down time willbe experienced.

Referring to FIG. 6, the bottom view of the switch 10 is shown and theleg portions 38 and 40 of the switch body 12 are shown as being hollowto receive the permanent magnets 20 and 22 movable therein. The magneticcore 24 is located centrally within the switch body 12 and engages anenlarged portion 41 of the clip 32 which is substantially in the middleof the clip. Outwardly extending gripping end portions 42 and 44 areformed on the clip 32 to dig into the material of the switch body andthereby be firmly held in place. This is best illustrated in FIG. 3which shows the gripping end portions 42 slightly embedded in thematerial of the switch body. Therefore, outward flexure of the legportions 38 and 40, as shown in FIG. 3, -will facilitate removal of theclip 32 for removing the magnetic core. In the alternative the grippingend portions 42 and 44 may engage recesses 43 and 45, respectively,formed within the switch body as shown in FIG. 7. In this case the clip32 is held in position by being confined at its lower end by therecesses and confined at its upper end by the presence of the coremember 24.

FIGS. 8 and 9 illustrate the operating condition of the keystem 14relative to the magnetic core 24. In FIG. 8 the keystem is in adeactuated up position and the permanent magnets 20 and 22 arepositioned immediately adjacent the magnetic core 24 to completelysaturate the magnetic material thereof. The retaining clip 32 has littleor no effect on diverting magnetic flux from passing through themagnetic core 24. However, upon actuation of the keystem 14 as shown inFIG. 9, the permanent magnets 20 and 22 are moved downwardly and themagnetic core 24 is substantially freed of all magnetic flux and ACcoupling can take place to cause a switching action.

Most advantageously, the retaining clip 32 is constructed ofparamagnetic material and now acts as a magnetic shunt between thepermanent magnets and 22 and the magnetic core 24 further to insure theswitching action. Any stray magnetic flux which would tend to enter themagnetic core 24 will be shunted by the metal clip 32. This featurehelps to create a more finite switching position or condition of thesolid state switching device as the keystem 14 is moved downward. Thatis, the keystem 14 moves downward to a definite position whereuponmagnetic flux is quickly diverted from the magnetic core 24 and fastswitching is accomplished by instantaneous transformer coupling betweenthe drive and sense wires 26 and 28.

What has been described is a simple and efficient solid state switchingdevice which can be completely mechanically connected and electricallyconnected to a keyboard structure and whereupon any failure of a switchcomponent will allow complete mechanical removal of the switch bodywithout necessitating disconnecting or unsoldering of the leadsconnected in circuit within the keyboard arrangement. Therefore,variations and modifications of this invention may be effected withoutdeparting from the spirit and scope of the novel concepts disclosed andclaimed herein.

The invention is claimed as followsi 1. In a solid state switchconstruction the combination including, a switch body having a recess, acore of magnetic material positioned within said recess, at least twowinding means passing through said core to have the ends thereofelectrically connected in a circuit when said switch body is mounted toa keyboard, movably mounted permanent magnet means positioned withinsaid switch body closely adjacent said core to saturate said core whenin one position and to be moved away from said core to unsaturate thesame when in another position, and clip means removably secured to saidswitch body over said recess firmly but removably to hold said corewithin said recess and to allow removal of said core from said switchbody without disconnecting said winding means from the circuit to whichit is connected when said switch body is removed from the keyboard.

2. The solid state switch construction of claim 1 wherein said clipmeans is formed of paramagnetic material, and said permanent magnetmeans moves adjacent said clip means when moved away from said core tofacilitate unsaturating of said core by providing a magnetic shunt pathbetween said permanent magnet means and around said core.

3. The solid state switch construction of claim 1 wherein said core ofmagnetic material is circular in configuration.

4. The solid state switch construction of claim 1 wherein said clipmeans is formed of a flat piece of paramagnetic material havingoutwardly extending gripping end portions thereof to be embedded intothe switch body in said recess, and removal of said clip means isaccomplished by flexure of the switch body to additionally open saidrecess.

5. A keyboard switch comprising, a saturable magnetic core, adepressable keystemhavin first and second legs extending on oppositesides 0 said core,

first and second permanent magnets mounted on said first and secondlegs, respectively, each permanent magnet being mounted on itscorresponding leg intermediate the leg and said magnetic core, saidpermanent magnets being positioned on said legs to be opposite said corewhen the keystem is not depressed, whereby a flux path is establishedfrom one said magnet to the other said magnet, and through said core tosaturate the same, said keystem carrying said permanent magnets out ofsaturating relation with said core when said keystem is actuated, andclip means removably engaged with said magnetic core to hold saidmagnetic core within said keyboard switch and to allow removal of saidmagnetic core without disconnecting the core from its associatedelectronic circuitry.

6. A keyboard comprising, a plurality of keyboard switches each havingan active and an inactive state and including, a saturable magnetic corehaving a closed loop magnetic flux path, a movable keystem having legportions on opposite sides of said magnetic core, first and secondpermanent magnets secured to said legs and movable with said keystem tosaturate said core when said switch is in one of said states with theflux passing through said magnetic core and to unsaturate said magneticcore when the switch is in the other of said states, coupling windingmeans positioned about said core to be connected in circuit withassociated circuitry, and clip means removably holding said magneticcore and its associated windings into the keyboard switch to allowremoval of the keyboard switch from said magnetic core and itsassociated windings without necessitating disconnecting of the windingsfrom its circuitry.

7. The keyboard of claim 6 wherein said clip means is formed of a flatpiece of paramagnetic material to form a magnetic shunt path with saidcore to divert the magnetic flux from said permanent magnets when saidswitch is in its active state.

8. The keyboard of claim 6 wherein said magnetic core is circular inconfiguration.

9. The keyboard of claim 6 wherein said clip means is formed of a flatpiece of material having outwardly extending end portions to be engagedinto recesses formed in the switch body.

1. IN a solid state switch construction the combination including, aswitch body having a recess, a core of magnetic material positionedwithin said recess, at least two winding means passing through said coreto have the ends thereof electrically connected in a circuit when saidswitch body is mounted to a keyboard, movably mounted permanent magnetmeans positioned within said switch body closely adjacent said core tosaturate said core when in one position and to be moved away from saidcore to unsaturate the same when in another position, and clip meansremovably secured to said switch body over said recess firmly butremovably to hold said core within said recess and to allow removal ofsaid core from said switch body without disconnecting said winding meansfrom the circuit to which it is connected when said switch body isremoved from the keyboard.
 1. IN a solid state switch construction thecombination including, a switch body having a recess, a core of magneticmaterial positioned within said recess, at least two winding meanspassing through said core to have the ends thereof electricallyconnected in a circuit when said switch body is mounted to a keyboard,movably mounted permanent magnet means positioned within said switchbody closely adjacent said core to saturate said core when in oneposition and to be moved away from said core to unsaturate the same whenin another position, and clip means removably secured to said switchbody over said recess firmly but removably to hold said core within saidrecess and to allow removal of said core from said switch body withoutdisconnecting said winding means from the circuit to which it isconnected when said switch body is removed from the keyboard.
 2. Thesolid state switch construction of claim 1 wherein said clip means isformed of paramagnetic material, and said permanent magnet means movesadjacent said clip means when moved away from said core to facilitateunsaturating of said core by providing a magnetic shunt path betweensaid permanent magnet means and around said core.
 3. The solid stateswitch construction of claim 1 wherein said core of magnetic material iscircular in configuration.
 4. The solid state switch construction ofclaim 1 wherein said clip means is formed of a flat piece ofparamagnetic material having outwardly extending gripping end portionsthereof to be embedded into the switch body in said recess, and removalof said clip means is accomplished by flexure of the switch body toadditionally open said recess.
 5. A keyboard switch comprising, asaturable magnetic core, a depressable keystem having first and secondlegs extending on opposite sides of said core, first and secondpermanent magnets mounted on said first and second legs, respectively,each permanent magnet being mounted on its corresponding legintermediate the leg and said magnetic core, said permanent magnetsbeing positioned on said legs to be opposite said core when the keystemis not depressed, whereby a flux path is established from one saidmagnet to the other said magnet, and through said core to saturate thesame, said keystem carrying said permanent magnets out of saturatingrelation with said core when said keystem is actuated, and clip meansremovably engaged with said magnetic core to hold said magnetic corewithin said keyboard switch and to allow removal of said magnetic corewithout disconnecting the core from its associated electronic circuitry.6. A keyboard comprising, a plurality of keyboard switches each havingan active and an inactive state and including, a saturable magnetic corehaving a closed loop magnetic flux path, a movable keystem having legportions on opposite sides of said magnetic core, first and secondpermanent magnets secured to said legs and movable with said keystem tosaturate said core when said switch is in one of said states with theflux passing through said magnetic core and to unsaturate said magneticcore when the switch is in the other of said states, coupling windingmeans positioned about said core to be connected in circuit withassociated circuitry, and clip means removably holding said magneticcore and its associated windings into the keyboard switch to allowremoval of the keyboard switch from said magnetic core and itsassociated windings without necessitating disconnecting of the windingsfrom its circuitry.
 7. The keyboard of claim 6 wherein said clip meansis formed of a flat piece of paramagnetic material to form a magneticshunt path with said core to divert the magnetic flux from saidpermanent magnets when said switch is in its active state.
 8. Thekeyboard of claim 6 wherein said magnetic core is circular inconfiguration.